Meri 5 saal ki beti nain sawal kiya ki jab Allah swt Imam Hussain as ko pyar kartay they unko itni berahmi se shaheed kaisay honay diya. Aur kya issey accha koi aur tareeqa nahin tha deen ko bachanay ka.
main usko kya jawab doon.

The love of Ahl bayt a.s. is the greatest asset we can ever have and pass on to the next generation specially our progeny to start off with.
Take it as a good sign that your five year old was concerned about Imam Hussein a s. and had to ask you this question.
You can explain you daughter going step by step with short sentences like,
Imam Hussein really loved Allah and out of this love, he promised he will do all that he can and should to.make people become good the way Allah wants.
He promised to Allah that he will be the best servant.
He knew that some people in this world are not good and infact very evil so whilst he was doing his best to guide them, they killed him.
Although he had all the powers to stop that, and also help was sent by Allah through thousands of Angles, but he wanted to do it with his own strength and energy like the normal people to show.them that they can keep.their promise to Allah in difficult times and be the best of servants even if they would face some kind of danger.
This way, Allah now has made him to be so beloved near everyone that until today we are remembering and crying for him.
This also shows how Allah loves him.